Understanding the Chemistry of Almond Flavor Australia AEM · •Although rancidity is a real...

Understanding the Chemistry of Almond Flavor

Alyson Mitchell PhDFood Science Department,University of California [email protected]

VII International Symposium on Almonds and PistachiosNov 5, 2017, Adelaide, South Australia

Almonds (Prunus dulcis)

•Botanically, the seed (fruit) of a drupe• Not a true nut

•A member of the rose family and is related to peaches, plums, apricots and cherries

•Native to the Middle East and South Asia• Consumed since the Early Bronze Age (3000‐2000 BCE)

•Convenient, dense source of energy that naturally stores well• Excellent source of Vitamin E (alpha tocopherol), high value protein, essential minerals and monounsaturated fats

•Consumption is associated with lowering LDL and a reduced risk of heart disease• Jenkins et al., Circulation. 2002; 106(11):1327‐1332

California Almonds

•California grows about 30 varieties of almonds• 80% of world almond production in 2015

•The three top almond varieties

• Nonpareil (39%)

• Monterey (12%)

• Carmel (9%)

Flavor

•Flavor is the sensory impression of a food

•Composite quality involving the sensations of aroma, taste, chemical irritation, as well as temperature, texture and sound

•Taste: Humans can distinguish 5 basic flavors• Sweet, sour, salty, bitter, and savory (umami)• Reactions with taste receptors on the tongue

•Aroma: Involves the interaction of volatile molecules with olfactory receptor neurons located in the nasal passageways

Raw Almonds

Raw Almond Taste

•Primary drivers of almond taste are fat, starch and sugars, and amygdalin

•Fat creates a rich taste

•Lack of acid enhances sweetness of starch and sugar

•Bitterness is derived from amygdalin

•Astringency from tannins (skin)

MacronutrientRange in CA‐grown

almonds(% g/g almond)

Lipids 35‐66

Protein 16‐23

Sugars 2.1‐7.4

Fiber 11‐14

Lipid Composition of Almonds

•The primary fatty acids in almonds are “Heathy fats”

•Oleic (18:1, 62−80%) and linoleic acid (18:2, 10−18%)

Name Number ofCarbons:Double

bonds

Percent in Almond Oil

Oleic 18:1 60-80%

Linoleic 18:2 10-18%

Palmitic 16:0 0.5-8%

Stearic 18:0 1-3%

•Non‐bitter (Sweet)• Sweet snacking almonds (creamy nutty flavor)

•Semi‐bitter• Often used in processing for their “marzipan‐like taste”

•Bitter • Middle East and Asia• Oils and flavorings• Contain amygdalin (3‐5%) and develop a cyanide aroma when moistened (chewed)• Can be toxic

Almond Phenotypes

A diglycoside

The disruption of almond tissue (e.g. chewing) enables amygdalin to come into contact with enzymes (b‐glycosidase) and form benzaldehyde and trace levels of HCN

Amygdalin

Benzaldehyde = amaretto flavor

Amygladin = bitter

-glycosidase

Chemical defensefor the plant

•Developed a sensitive method (UHPLC (ESI)‐MS/MS) to measure amygdalin in almonds • Understand levels in CA varieties and breeding stocks

•Commercial non‐bitter (sweet) varieties• Average amygdalin content 63.13 ± 57.54 mg/kg

•Semi‐bitter (UCD)• Average amygdalin 992.24 ± 513.04 mg/Kg

•Bitter (UCD)• Average amygdalin 40,060.34 ± 7,855.26 mg/kg

•Additional applications alcoholic bitters•USDA recall of almonds

Amygdalin in California Almonds

Lee et al., J. Agric. Food Chem. 2013, 61, 7754−7759

Amygdalin in California Almond Varieties

Lee, et al., J. Agric. Food Chem., 2013, 61 (32), pp 7754–7759

•Volatile molecules are responsible for the aroma of almonds

•The predominant almond aroma compound is benzaldehyde• Cherry, almond flavor• Artificial almond aroma

•Comes from the breakdown of amygdalin

Raw Almond Aroma

Measuring Volatile Aroma Compounds in Almonds HS‐SPME GC/MS

Gas Chromatography

Samples are agitated at 500 rpm and pre‐equilibrated at 40ºC for 45 min, after which they were extracted with a 1 cm 30/50um StableFlexDVB/CAR/PDMS fiber exposed for 45 mins at 250 RPM

5 g sample is placed in a 20‐mL SPME vial

Chromatogram

Amygdalin and Benzaldehyde in California Almonds

•Strong correlation between amygdalin levels and benzaldehyde levels

In preparation K. Lau

Flavor and Variety

•Benzaldhyde ranges between 0.587‐17.995 mg/kg in commercial almonds

Variety Classification type Average amygdalin (mg/kg)

Average benzaldehyde(mg/kg)

Aldrich California 76.50 ± 23.99 a 17.995 ± 5886.7 aFritz California, Mission 59.71 ± 12.37 ab 11.315 ± 2795.5 bPadre California, Mission 53.24 ± 16.74 bc 8.806.8 ± 4101.5 bcMonterey California 46.76 ± 15.21 bc 8.654.3 ± 2137.3 bcWood Colony California 41.49 ± 14.41 bcd 7.703.4 ± 3394.5 bcMission Mission 40.24 ± 18.40 cd 6.489 ± 2503.4 cdCarmel California 26.42 ± 14.30 de 5.656.9 ± 1845.3 cdeButte California 18.56 ± 20.77 ef 2.768.3 ± 1783.2 defNonpareil Nonpareil 9.11 ± 4.42 ef 1.939.5 ± 1318.9 efSonora California 5.56 ± 2.20 f 1.936.4 ± 1602.1 efAvalon 3.00 ± 4.17 f 1.179.6 ± 488.1 fIndependence 2.07 ± 1.66 f 1.062 ± 871.4 fWinters California 1.62 ± 2.10 f 0.730.6 ± 633.3 fPrice California 1.77 ± 1.74 f 0.587.7 ± 272.9 f

Raw Almond Aromaliterature review

Type Compound Aromaa Sourceb

Alcohol 1,2‐propanediol nd 2, 31‐butanol medicine, fruit, wine 2, 3, 41‐heptanol herb 2, 71‐hexanol resin, flower, green 1, 2, 3, 7, 41‐Nonanol aldehydic, waxy, citrus 7, 31‐octanol chemical, metal, burnt 2, 3, 7, 41‐pentanol fruity 1, 2, 3, 5, 62‐ethyl‐1‐hexanol sweet, floral, oily 1, 3, 2‐heptanone cheesy, banana, fruity 1, 22‐methyl‐1‐propanol wine, whisky 2, 3, 7Benzyl alcohol floral, phenolic 1, 3, 4, 5, 6, 72‐phenylethanol floral, hyacinth/gardenia 5, 7, 6, 1, 3

3‐methyl‐1‐butanol malt 2, 3, 73‐methyl‐2‐Buten‐1‐ol fruity, alcoholic, green 5, 7, 6 ,33‐Methyl‐3‐Buten‐1‐ol nd 3, 5, 6

Pyrazine 2‐Methylpyrazine roasted 1, 4Acids Acetic acid sour 8, 3

hexanoic acid sweaty, rancid 2, 3Terpenes alpha‐pinene piny 7, 2

limonene orange peel 2, 7Aldehydes Benzaldehyde sweet, marzipan 1, 3, 2, 7, 5, 6, 4

heptanal ranid, pungent 1, 2, 7, 4Hexanal grassy, fatty, rancid 1, 8, 2, 3, 5, 7, 6Nonanal soapy, fatty, rancid 8, 2, 3, 7, 4Octanal soapy, fatty, rancid 8, 2, 7pentanal almond, malt, pungent 1, 2

Lactone butyrolactonec creamy, oily, fatty 2, 3Alkane Toluene painty 4, 7, 5, 6Sulfur‐containing Methional cooked potato 8, 4

• Volatile compounds identified in raw almonds and reported in 2+ studies

• Benzaldehyde, benzyl alcohol and hexanal are the most widely detected volatiles in raw almonds

• Other key volatiles include: pentanol, hexanol, 2‐phenylethanol, 3‐methyl‐1‐butanol, 3‐methyl‐2‐buten‐1‐ol, and nonenal

•Butte/Padre almonds (7 months in storage)

•Raw almond aroma intensity is low with exception of benzaldehyde

•Identified (41): 13 carbonyls, 1 pyrazine, 20 alcohols, and 7 additional volatiles

Raw Almond Aroma

Xiao et al., J. Food Chemistry 151 (2014) 31-39

Compound Content PPB Aroma

Benzaldehyde 2,934.6 ± 272.5 sweet, marzipan

3‐Methyl‐butanal 86.4 ± 3.3 alcoholic, fruity, whiskey, banana

3‐Methyl‐2‐butenol 17.3 ± 0.9 fruity, green, lavender

Benzyl alcohol 3.9 ± 0.0 floral, phenolic

Hexanal 422.6 ± 97.9 grassy, fatty, rancid

Roasted Almonds

Roasted Almond FlavorRoasting = Flavor Development

•When almonds are roasted they undergo chemical reactions that lead to the creation and release of volatile compounds

•Heating generates new volatiles through lipid oxidation, sugar pyrolysis, and the Maillardreaction• Malty, roasted, chocolate, nutty flavors

•Range and levels of volatiles formed will depend upon the roasting conditions

•Common temperatures used for dry roasting range from 130°C to 150°C

•We roasted almonds under controlled conditions of 138 °C for 38 min

•17 Additional volatile compounds were identified • pyrazines, furans, alcohols, pyrroles, ketones, aldehydes, and aromatic hydrocarbons

•Pyrazines, furans and alcohols are key components of roasted almond flavor• Pyrazines: Maillard sugar‐amine reactions and Strecker degradation • Furan‐containing compounds: thermal degradation of sugars• Alcohols and aldehydes: lipid oxidation

Volatiles in Roasted Almonds


Changes in Volatile PyrazinesRoasted Nutty Aromas

almond; green; meaty; coffee

meaty; nutty; medicinal; woody

butter; musty; woody; nutty

peanut

chocolate; meaty; nutty; green

chocolate; meaty; nutty; green

musty, potato, cocoa, nutty

Changes in Volatile Aldehydes and Keytones

[chocolate/nutty][chocolate][sweet/butter]

[almond/green leaf][rummy/nut][buttery]

[brown/caramel][aldehydic][almond/marzipan]

[green][honey/floral]


Changes in Volatile Alcohols

Rancidity in Almonds

Rancidity

•Rancidity is the unpalatable odor and flavor of deteriorating edible fats and oils in foods

•Rancidity occurs via two chemical reactions:

•Oxidation • Oxygen attack of the triglycerides

•Hydrolysis• Addition of water across triglycerides and release of Fatty acids (FFAs)

Robards et al., Analyst, 1988 v 113

•Rancidity in almonds occurs primarily via the oxidation of oleic [18:1] and linoleic [18:2] acids• Initiated by exposure to heat (e.g. pasteurization, blanching, roasting, etc.,), moisture and/or oxygen (e.g. during storage)

•A problem associated with storage and humidity

•Occurs in raw and roasted almonds

Rancidity in Almonds

Measuring Rancidity in Almonds

•Although rancidity is a real problem confronting processors, there is no completely objective chemical method for determining rancidity• Industry relies on several methods for routine estimates of oxidation however, there is no uniform or standard method for detecting oxidative changes

•Challenges:• Lipid oxidation is a dynamic process and levels of chemical markers of lipid oxidation change throughout the lipid oxidation process

• Little is known regarding correlations between chemical measures of rancidity and consumer acceptance/perception of almonds

•Free Fatty Acids (FFA): •Measures the hydrolytic or enzymatic release of FFAs • FFAs are more susceptible to oxidation

• Industry standard is < 1.5% FFAs

•Found to correlate with sensory evaluation in butter•No studies in almonds

Chemical Measures moving analytical targets


Peroxide Value (PV) ◦ Lipid peroxides are the first product of lipid oxidation and are used as an indicator of early oxidative changes

◦ Almonds PV < 5 meq/Kg is considered the benchmark

However:◦ PV levels decrease as oxidation progresses and lipid peroxides break down◦ Low levels can be present when there is extensive lipid oxidation

•Conjugated Dienes (CDs)•Measures initial stages of rancidity•Oxidized linoleic acid rearranges to form a CD• CDs absorb UV light at 232–234 nm which can be measured

•However:• CD levels can decompose as oxidation progresses •No industry values for CDs for almonds



•Head Space Volatiles •Measures the later stages of oxidation• After lipid hydroperoxides breakdown

•Hexanal•Most commonly measured •No industry standard for hexanal in almonds• A wide range of volatile compounds exist in raw, roasted, and stored almonds

Linking Rancidity with Consumer Linking

•Monitor these markers of lipid oxidation and volatile aroma profiles in light and dark roasted almonds undergoing accelerated shelf‐life conditions that promote rancidity development over 12 months

•Measured the consumer hedonic response (degree of liking) of these almonds to determine how consumer liking correlates with the chemical measures during rancidity development during accelerated shelf‐life storage

Samples

•De‐hulled, raw Nonpareil almonds (2014 Harvest year)

•Almonds were dry roasted at • 115 ± 6ºC for 60 min to achieve a light roast • 152 ± 6ºC for 15 min to achieve a dark roast

•Almonds were stored at 39 ±1ºC and RH of 15% ±1 for 12 months

•Almonds were randomized and stored in open bags to maximize oxygen exposure during storage

•Almonds were sampled every month (30 days)

Analytical Correlations

• Hydrolytic Rancidity• Free Fatty Acids (FFA)

• Primary Oxidation Products• Peroxide Value (PV)• Conjugated Dienes (CD)

• Vitamin E• Tocopherols (and )

• Volatiles by SPME‐HS GC/MS• Sensory Measures

• Consumer Hedonic Analysis

Consumer Hedonic Analysis

•Untrained consumers (99) between 14 and 80 and who consumed almonds at least once a month (not pregnant)

•Consumers were served samples of 6‐7 almonds coded with randomly generated 3‐digit numbers as sample identifiers

•Consumers indicate their liking of samples by marking a 9‐pt hedonic scale with accompanying phrases as anchors

Hedonic Ratings

•Significant differences in liking related to the storage time ◦ Consumers had a significant difference in liking between samples aged 0, 2, 4, and 6

months, while there was no significant difference found between samples aged 6, 8, and 10 months

•No significant difference was found in liking related to roast level

*A rating of 5 indicates that the consumer is indifferent to the product and below this begins to dislike the product

Correlation with Measures of Lipid Oxidation Light Roast Almonds

Storage Time

Analysis 0 months 2 months 4 months 6 months 8 months 10 months 12 months

Peroxide Value (mEq/g oil)

0.57 ± 0.04e

1.13 ± 0.14d

1.38 ± 0.20d

2.84 ± 0.02b

2.14 ± 0.18c

2.70 ± 0.08b

1.26 ± 0.08d

Free Fatty Acid Value (% oleic)

0.21 ± 0.00d

0.25 ± 0.00 cd

0.28 ± 0.00bc

0.31 ± 0.01abc

0.32 ± 0.02ab

0.36 ± 0.03a

0.36 ± 0.03a

Conjugated Dienes (%)

0.213 ± 0.000f

0.222 ± 0.00f

0.255 ± 0.000cd

0.242 ± 0.003e

0.261 ± 0.008bc

0.267 ± 0.002b

0.302 ± 0.001a

Alpha Tocopherol Conc. (mg/kg oil)

435 ± 4a

424 ± 16a

406 ± 1abc

387 ± 3bcd

362 ± 4 def

363 ± 32def

334 ± 11f

Beta + Gamma tocopherol Conc.

(mg/kg)

34.3 ± 0.5ab

34.0 ± 0.2ab

34.1 ± 0.3ab

32.8 ± 0.5ab

31.9 ± 0.4ab

33.5 ± 1.0ab

31.7 ± 0.9ab

Mean Consumer Hedonic Score 7.4 ± 1.4 a 6.6 ± 1.5 b 5.8 ± 1.55 c 4.9 ± 1.9 d 4.9 ± 2.0 d 4.7 ± 2.1 d

Correlation with Measures of Lipid Oxidation Dark Roast Almonds

Storage TimeAnalysis 0 months 2 months 4 months 6 months 8 months 10 months 12 months

Peroxide Value (mEq/g oil)

0.61 ± 0.04 n

2.21 ± 0.12 m

3.96 ± 0.07l

11.36 ± 0.23j

16.07 ± 0.53 g

16.48 ± 0.18 g

13.00 ± 0.03i

Free Fatty Acid Value (% oleic)

0.20 ± 0.03j

0.18 ± 0.00 i

0.37 ± 0.01 g

0.36 ± 0.01e

0.42 ± 0.04 c

0.54 ± 0.04 c

0.57 ± 0.04 a

Conjugated Dienes (%)

0.216 ±0.001 j

0.238 ±0.001 i

0.286 ±0.002 g

0.362 ±0.001 e

0.464 ±0.003 c

0.464 ±0.002 c

0.508 ±0.001 a

Alpha Tocopherol Conc. (mg/kg oil) 444 ± 1 a 418 ± 7 ab 396 ± 2 bc 358 ± 8 de 328 ± 8 fg 277 ± 6 h 292 ± 9 h

Beta + Gamma tocopherol Conc.

(mg/kg)

35.0 ± 0.1 a

34.0 ± 0.8 abcd

34.4 ± 0.5 ab

32.3 ± 0.3 cdefg

32.0 ± 0.6efg

31.0 ± 0.1 g

31.2 ± 1.3 fg

Mean Consumer Hedonic Score 7.2 ± 1.7 a 6.8 ± 1.4 b 5.8 ± 1.7 c 4.7 ± 2.0 d 4.5 ± 2.0 d 4.2 ± 2.0 d

Peroxide Value

Franklin et al., J. Agric. Food Chem. DOI: 10.1021/acs.jafc.6b05357‐ 2017

Peroxide Value:• < 5.0 is a recommended industry rejection

standard. • None of the light roast samples were greater

than 5.0, despite consumer indifference/dislike• Doesn’t correlate with consumer liking

Free Fatty Acids

0.00

0.25

0.50

0.75

1.00

0 2 4 6 8 10 12Sample Age (months)

Free

Fat

ty A

cids

(% O

leic)

RoastDR

LR

Free Fatty Acids


Free Fatty Acids:• < 1.5% Oleic is a recommended industry rejection

standard. • No samples were greater than 1.5% Oleic, despite

being consumer indifference/dislike• However roasting would inactivate lipase enzymes

Conjugated Dienes


Conjugated Dienes:• No industry standard currently exists for CD.• There was very little change in light roast

samples, despite consumer indifference/dislike at 6 months

• Correlates with consumer liking however sensitivity is low

Alpha Tocopherol (Vitamin E)


Tocopherols:• alpha tocopherol decreased by 34.3 % (DR)

and 23.2% in LR almonds• Undergoing oxidation

Volatile Compounds

•A total of 99 volatile compounds were identified in roasted almonds over the 12 months of storage

•Compounds include: 8 acids, 17 alcohols, 19 aldehydes, 5 alkanes, 4 esters, 11 ketones, 13 pyrazines, 3 terpenes and 20 other compounds

•Authentic standards were available to confirm identifies of 63 compounds

•Tentative identities of the remaining 36 compounds were made by comparing MS spectra with the NIST Library and calculated Kovat’s retention indices (KI) with literature values of standards chromatographed under comparable conditions

Trends in Total Volatiles by Class

Flavor fade and lipid oxidation are observed at 6 month

Name Correlation Value 0 Months 2 Months 4 months 0 Months 2 Months 4 months

Positive Correlations

methoxymethyl oxirane 0.939 3.7 ± 0.0 2.27 ± 0.03 1.18 ± 0.04 4.73 ± 0.25 2.80 ± 0.05 1.33 ± 0.03

ethylpyrazine 0.921 5.56 ± 0.08 3.45 ± 0.09 2.79 ± 0.10 5.11 ± 0.15 3.28 ± 0.04 2.87 ± 0.05

2,3-dimethylpyrazine 0.918 3.67 ± 0.04 2.36 ± 0.11 1.77 ± 0.02 3.22 ± 0.04 2.05 ± 0.21 1.87 ± 0.08

2-ethyl-6-methylpyrazine 0.908 5.41 ± 0.10 3.59 ± 0.10 2.97 ± 0.13 4.24 ± 0.17 3.16 ± 0.06 2.93 ± 0.04


3-methylbutanal 0.886 92.9 ± 0.8 64.4 ± 0.89 19.6 ± 1.09 114 ± 1.19 46.4 ± 1.04 20.3 ± 0.63

2-methylbutanal 0.884 225 ± 3 146 ± 2.37 43.7 ± 0.691 260 ± 4.84 106 ± 1.82 47.9 ± 1.17


2-ethyl-5-methylpyrazine 0.861 2.11 ± 0.06 1.35 ± 0.03 1.12 ± 0.04 1.51 ± 0.03 1.18 ± 0.024 1.12 ± 0.01

methylpyrazine 0.855 44.6 ± 1.78 21.8 ± 0.48 15.8 ± 0.58 35.5 ± 0.57 17.4 ± 0.25 15.4 ± 0.20

pyrazine 0.842 2.49 ± 0.14 1.19 ± 0.04 0.917 ± 0.03 2.41 ± 0.04 0.984 ± 0.04 0.833 ± 0.01

Select compounds that decrease with significant correlation(r2 > 8.4) and correspond with consumer liking

Concentration in DR Concentration in LR

Name Correlation Value 0 Months 2 Months 4 months 0 Months 2 Months 4 months

Negative correlations

hexanoic acid -0.900 1.05 ± 0.06 14.7 ± 3.00 59.8 ± 2.11 1.96 ± 0.32 12.3 ± 0.15 56.3 ± 1.22

pentanal -0.902 3.92 ± 0.04 62.8 ± 0.59 110 ± 1.26 5.5 ± 0.06 41.3 ± 0.84 111 ± 0.79

hexanal -0.902 58 ± 0.34 716 ± 16.30 1360 ± 15.9 77.9 ± 1.8 492 ± 9.25 1390 ± 8.25

2-pentylfuran -0.909 4.86 ± 0.14 13.9 ± 0.23 28.8 ± 0.58 6.48 ± 0.33 16.3 ± 0.42 32.4 ± 0.35

2-hexenal -0.922 0.393 ± 0.01 2.93 ± 0.17 5.13 ± 0.27 1.23 ± 0.01 2.67 ± 0.02 5.28 ± 0.03

2-heptenal -0.928 0.799 ± 0.03 6.51 ± 0.23 17.6 ± 0.32 1.1 ± 0.057 5.12 ± 0.07 19.2 ± 0.34

1-butanol -0.931 0.542 ± 0.03 1.48 ± 0.03 2.78 ± 0.07 0.623 ± 0.01 1.05 ± 0.02 2.62 ± 0.02

3-octen-2-one -0.934 0.465 ± 0.01 5.58 ± 0.15 17.2 ± 0.34 0.755 ± 0.05 5.6 ± 0.09 14 ± 0.35

styrene -0.943 1.53 ± 0.02 3.85 ± 0.05 5.02 ± 0.17 1.79 ± 0.05 2.47 ± 0.05 5.28 ± 0.02

1-pentanol -0.946 3.79 ± 0.06 16.8 ± 0.22 36.9 ± 0.81 6.31 ± 0.14 11.7 ± 0.13 34.6 ± 0.27

Select compounds that increase with significant correlation(r2 > 9.4) and correspond with consumer liking

Concentration in DR Concentration in LR

Compounds with significant correlation with consumer liking (p <0.05) and an absolute regression slope of >2 μg/kg change in concentration

per unit liking

Compound Name Linear R2

valueSlope of Conc. (μg/kg) vs. liking

Aroma Quality Aroma Threshold (μg/kg)

DR

4 month

DR 6

month

LR

4 month

LR

6 month

heptanal 0.952 ‐82.55 fatty, oily, powerful, rancid, citrus, sharp

501,O 85.4 ± 2.0 187 ± 3 87.1 ± 0.9 137 ± 2

octanal 0.885 ‐93.24 citrus‐like, soapy, penetrating

551,O 69.5 ± 1.5 158 ± 5 69 ± 1 127 ± 3

hexanal 0.814 ‐736.91 fatty, green, grassy 751,O 1360 ± 15.9 2380 ± 34.6 1390 ± 8.25 1480 ± 6.5

1‐octen‐3‐ol 0.753 ‐11.27 mushroom, earthy, green, oily, fungal

14,W 7.29 ± 0.237 14.9 ± 0.365 5.75 ± 0.158 10 ± 0.207

benzaldehyde 0.586 2.53 artificial almond, sweet, cherry

350W 8.79 ± 0.334 10.6 ± 0.568 9.1 ± 0.0877 8.71 ± 0.195

furfural 0.631 4.63 sweet, woody, almond, bread

3,0004,W 5.2 ± 0.219 3.95 ± 0.12 4.55 ± 0.0394 3.78 ± 0.0424

2‐methylbutanal 0.781 83.19 fruity, dry, slightly green, chocolate, nut

105,O 43.7 ± 0.691 23.1 ± 1.8 47.9 ± 1.17 18.8 ± 0.159

3‐methylbutanal 0.785 35.66 musty, chocolate, nutty, malty

5.45,O 19.6 ± 1.09 11.2 ± 0.675 20.3 ± 0.63 8.28 ± 0.141

Conclusions

•Raw almond flavor is dominated by amygdalin and benzaldehyde

•Attributes of roasted almond flavor include: pyrazines, furans and alcohols, furfural, and especially 2‐methylbutanal and 3‐methylbutanal

•In stored roasted almonds the PV does not relate to consumer liking and 5 mEq/kg is not a good measure of rancidity development or consumer acceptance

•FFA remain below recommended 1.5% oleic indicating this is not a good measure of rancidity development or consumer acceptance of roasted almonds

•Consumer liking was not different based on roast level • Consumers changed liking significantly by 2 months, by 4‐5 months consumers neither liked nor disliked the almonds • Consumers disliked almonds on average by 6 months for both LR and DR

•At 2 months, significantly decreases were observed in compounds related to roasted flavor (pyrazines) indicating that flavor fade occurs rapidly

•At 6 months significant increases in aldehydes were observed with the strong correlations with heptanal, octanal and hexanal

Acknowledgements

UC Davis •Lillian Franklin, M.S.•Suthawan Charoenprasert, PhD

Food Safety and Measurement FacilityAnna Hjelmeland, PhDSusan Ebeler, PhD

Almond Board of California• Guangwei Huang, PhD

Blue Diamond Almonds• W. Scott Moore• Steven Phillips• Brian Dunning

Agilent Technologies• Phil Wylie, PhD

• John Kinsella Endowment / Almond Board of California

Understanding the Chemistry of Almond Flavor Australia AEM · •Although rancidity is a real...

Documents

Transcript of Understanding the Chemistry of Almond Flavor Australia AEM · •Although rancidity is a real...